A new approach to internal Lewis pairs featuring a phosphenium acid and a pyridine base

Abstract

A bis(imino)acenaphthene (BIAN) ligand containing a pendant Lewis base has been used as a new framework to support a N-heterocyclic phosphenium cation (NHP). Reactivity studies demonstrate the ability of the ligand to act as a Lewis base, while the phosphorus centre provides a Lewis acidic site, giving new opportunities in NHP chemistry.

Lewis Base Stabilized Oxophosphonium Ions

“…[54] Indeed, analysis of crystals of [ (15) ) was found to be shorter than that in O=PPh 3 (1.491 (2) ), [55] thus suggesting the cationic nature of the phosphorus center. The PÀN distances in the heterocycle (N1-P1 1.6306(18) and N2-P1 1.6345 (19) ) are only slightly different to those of [1][GaCl 4 ] (N1-P1 1.6103 (14) and N2-P1 1.6128 (14) ). The P-N distance to the trimethylamine fragment is much longer (N3-P1 1.8431 (19) ), thus indicating the possible dative nature of the interaction between the nitrogen lone pair to the phosphorus cation.…”

“…The PÀN distances in the heterocycle (N1-P1 1.6306(18) and N2-P1 1.6345 (19) ) are only slightly different to those of [1][GaCl 4 ] (N1-P1 1.6103 (14) and N2-P1 1.6128 (14) ). The P-N distance to the trimethylamine fragment is much longer (N3-P1 1.8431 (19) ), thus indicating the possible dative nature of the interaction between the nitrogen lone pair to the phosphorus cation. There are few examples in the literature to compare this P À N interaction with, the closest being [4-dimethylaminopyridine-PPh 2 ] + , for which the pyridine N À P distance (1.789 (1) ) is shorter than that seen in [2] + .…”

“…[1] There have been regular contributions [2][3][4][5][6] to the area of N-heterocyclic phosphenium ions A since the first reports 30 years ago. [7,8] The area has seen a recent resurgence [6,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] which may be due to the popularity of the isovalent singlet carbenes and, as such, the use of phosphenium ions as ligands in transition metal chemistry has been exploited. [24][25][26][27][28][29][30] In the context of main group chemistry, [31] phosphenium ions have been involved in the preparation of phosphinophosphonium systems, [32][33][34][35][36][37][38][39][40] as well in reactions with P 4 , [39,[41][42][43][44] and other reagents.…”

A Tale of Two Elements: The Lewis Acidity/Basicity Umpolung of Boron and Phosphorus

“…Subsequently, Ragogna et al. synthesized a unique intramolecular FLP comprised of an NHP and a pendant lutidine donor 30 . The Lewis acidic P cation was shown not to form an adduct with PMe 3 or pyridine, although the 4‐ N , N ‐dimethylaminopyridine (DMAP) adduct 31 was obtained (Scheme ).…”

Eine Geschichte über zwei Elemente: die Umpolung der Lewis‐Acidität/Basizität von Bor und Phosphor

“…Später synthetisierten Ragogna et al. ein einzigartiges intramolekulares FLP 30 , das aus einem NHP und einem angekuppelten Lutidindonor bestand . Zwar bildete das Lewis‐acide P‐Kation mit PMe 3 oder Pyridin kein Addukt, allerdings konnte das 4‐ N , N ‐Dimethylaminopyridin(DMAP)‐Addukt 31 erhalten werden (Schema ).…”